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We report enhanced photorefractive sensitivity in Mn, Ce doped LiNbO3 at 514 nm and 633 nm under ultraviolet illumination at 365 nm. Without ultraviolet sensitization, the crystal showed very weak diffraction efficiency and self-erased behavior. The accumulation of charged states by ultraviolet light is observed even after the hologram is erased because of the asymmetric process of recording and reading. The concentrations of doped ions and the intensity ratio of ultraviolet and recording light are important factors to improve sensitivity in this material.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Computers have enabled the generation and acquisition of large vector and tensor data-sets. Reynolds numbers, and in data acquisition producing large data-set such as weather and ocean current databases. However, techniques for automated searching and comparison of large vector and tensor data-sets have been lacking. Many of the techniques are based on visual comparisons which do not have the quantitative rigor required for automated comparisons. Other methods which use data based comparisons require a common domain, grid alignment, and interpolation often making data- sets acquired from different sources difficult to compare. This paper provides comparison methods that are based on the topology of the vector field. These methods can be used for both 2D and 3D fields, and depending upon the complexity of the field, different levels of comparisons can be utilized to reduce search times. Topology based methods have the added benefits of describing a field that is independent of the grid, and that is based solely on topological components which have a significant compression over the original field.

Summary form only given.Volume holographic recording of information is an attractive solution for the next generation of digital storage, holding promise for systems with high density (/spl ges/10 Gbit/cm/sup 2/), and fast transfer rate (Gbit/sec). The performance of a holographic storage system is principally determined by the recording medium characteristics. Photorefractive crystals had been the most extensively investigated volumetric media, offering good optical quality, and sensitive, but typically volatile, recording. Recently, advances in sufficiently thick photopolymerizable recording media have provided a very attractive alternative for WORM systems. This work evaluates the recording physical properties of photopolymer holographic storage.

Summary form only given.Holographic data storage records information in the form of volumetric gratings within the volume of the recording medium. In digital holographic storage information is typically encoded in the form of data pages, which includes modulation coding, data shuffling, and error correction. Selective properties of volumetric gratings allow for a multitude of holograms to be recorded in virtually the same volume through angular, wavelength, or shift and correlation multiplexing techniques. Potentially high data density and transfer rates (which are due to highly parallel access to the stored data) have been a topic of intense research and development. Short data seek time ( 100 Gbit per 6.5' disk).

Its useful capacity, transfer rate and access time measure the performance of a holographic data storage system (HDSS). Data should never be lost, requiring a corrected bit error rate (BER) of 10-12 to 10-15. To compete successfully in the large storage marketplace, an HDS drive should be cost-competitive with improved performance over other drives. The exception could be certain niche markets, where unique HDS attributes — all-solid-state implementation with extremely short access times or associative retrieval — are attractive or required.

The physical properties of photopolymer grating formation are, for the first time, investigated elaborately with respect to I, and (Lambda) . The dynamics of holographic recording with constant exposure energy (15mJ/cm2), are evaluated for a wide range of different I (mW/cm2 - W/cm2), and for a few typical (Lambda) (0.5 - 3.5 micrometer), in a material utilizing cationing-ring-opening polymerization (Polaroid CROP ULSH-500B). Diffusion was evaluated to limit the photo- initiated recording sensitivity at high I(greater than W/cm2 approximately (Lambda) -2). At the same time, however, the significant post-exposure grating development observed for diffusion limited recordings, was identified to allow eventually for equally high sensitive final gratings (approximately 3 - 5 cm/mJ) without reciprocity, or diffusion limitations. Based on these observations, a new physical model was developed that describes more accurately holographic recording utilizing photo-initiated polymerization, and accounts successfully for the observed physical properties of grating formation.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We evaluate the physical properties of volume holographic recording in photopolymer that allow for high performance nonvolatile digital data storage. We identified efficient volume grating formation for photoinitiated cationic-ring- opening polymerization that utilizes unrestricted monomer diffusive transport contributions in the grating development process during and after exposure.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Volume holographic recording of information is an attractive solution for the next generation of digital storage systems, for the ability to optically record and retrieve, independently, multiple superimposed holograms, transferring in parallel the corresponding page-formated digital data representations. Due to these two unique properties, a holographic digital data storage (HDDS) system holds promise for high capacity density (Tb/cm 3 ), and fast transfer rate (Gb/sec) [1]. During holographic recording, information is stored as refractive index modulation, i.e. volume phase gratings, resulting from the interference of the information-bearing and reference laser beams within the volume of the holographic recording medium. The performance of a holographic storage system is principally determined by the physical characteristics of the recording medium [2]. Photorefractives have been the most extensively investigated materials utilized in holographic storage. Recently, advancements in sufficiently thick photopolymer holographic media have provided a promising alternative for WORM systems [3, 4]. In these materials, formation of compositional volume phase gratings through a photoinitiated polymerization process provides an attractive recording mechanism which allows for relatively large permanent refractive index modulation with high recording sensitivity, that compares favorably to, typically volatile, recording in photorefractives [4, 5, 6]. Limitations in the response of these materials, however, may arise during and after exposure, limiting the sensitivity, the final grating strength, and the digital system performance. In this presentation, we evaluate the physical properties that allow for efficient volume holographic recording utilizing photoinitiated polymerization grating formation. The previous studies of photoinitiated polymerization recording, in materials utilizing a free-radical [4], or a cationing-ring-opening (crop) [7] process, have suggested limited grating strength to arise due to reciprocity failure at high intensity, and at large grating spacing recordings. Grating formation has further been described through a photoinduced reaction diffusion model that ignores postexposure polymerization (dark reaction), and introduces diffusion limited response for multiple recordings [4]. In this presentation, we evaluate photopolymer recording in a unified framework based on the polymerization (τ p ) and the diffusion (τ d = Λ 2 /D) time scales that completely characterize the principal physical processes during grating formation [8]. We investigated elaborately holographic recording in a material utilizing cationing-ring-opening polymerization (crop Polaroid samples).

A three-dimensional auto-correlation function is proposed as a tool to analyse 3-D fluid flow datasets. In order to test this concept, we analysed time and space evolving datasets obtained from visualizations of the flow over a half-span delta wing. The processed slices show that the regions with strong vortical motion can easily be detected. However, it is much more difficult to determine the cross-stream velocity components. Obviously, some aspects need more attention before we can decide on the usefulness of this technique: (1) the effect of resolution and noise; (2) the smoothness of the smoke field must be controlled in order to get a large grey scale value variance; (3) the time interval between two recordings must correspond to the time scale of the cross stream motions; (4) the test flow must be less complex.

Lead barium niobate (Pb1-xBaxNb2O6, PBN1-x) is a very promising photorefractive material for applications such as holographic data storage. We investigate the light induced absorption, photorefractive properties, such as the sensitivity, diffraction efficiency, and gain, and thermal fixing properties in Ce doped tetragonal PBN50, and compare with the properties of an undoped PBN sample. Non-single photon behavior was observed only in Ce doped sample, but not in the undoped sample. Thermal fixing was achieved in both undoped and Ce doped samples at temperatures above 70oC. The room temperature life times after thermal fixing were estimated to be 30 hours and 20 days for undoped and Ce doped samples, respectively.

Optically gated recording and nonvolatile readout in a digital volume holographic data storage system that uses a pair of mutually incoherent light sources during recording and only one for readout were demonstrated recently. This approach used stoichiometric lithium niobate, which after post-growth processing gave rise to an at least two orders of magnitude improvement in sensitivity over the best materials reported previously. It is also shown that by adding certain dopants (iron and manganese) to near-stoichiometric lithium niobate, the dark storage time and gating efficiency can be increased compared with previous work. The underlying physical mechanisms of gated recording and the effectiveness of the gating process responsible for this manifold improved performance are discussed, and bipolarons and small polarons are identified as the responsible photorefractive species.

The performance of holographic storage in photopolymer recording media gets limited by compositional volume grating distortions, arising primarily due to postrecording anisotropic medium dimension changes. We evaluate the polymer grating distortions, and the corresponding diffraction efficiency fluctuations, as noise in the holographic digital system. The analysis suggests the importance of the distortion induced grating strength fluctuations relative to optical scattering from the system performance, and encoding, characteristics at different grating distortion regimes.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

By reading data in an angular multiplexed holographic storage system at a wavelength other than the wavelength used for writing, the problem of unwanted erasure can be prevented. By compensating data prior to recording, the mismatch resulting from the difference in reading and writing wavelengths may be minimized. Such a compensation technique was experimentally investigated by recording differentially encoded data within an Fe doped sample of LiNbO3 at a wavelength of 514 nm and recalling data using 488 nm. Our system demonstrated that the recording of compensated data allowed accurate readout with a raw bit error rate of .08%.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We investigated compositional volume grating formation in the Polaroid medium that utilizes the cationic-ring-opening photoinitiated polymerization process, and compared our conclusions with the current physical model describing polymer holographic recording. We identified the effects of diffusion and polymerization during illumination, as well as significant postexposure grating development. Holographic recording in this medium allows for final strong gratings with high recording sensitivity (S approximately 2 cm/mJ), that were not limited at the higher recording intensities (I less than or equal to 250 mW/cm2) corresponding to photon (exposure) limited recording. The results of the present analysis allow for more comprehensive physical description of grating formation in the photoinitiated CROP process, and evaluation of the polymer recording process in a nonvolatile holographic storage system.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Recording of holographic gratings by 532-nm laser pulses in photochromic bulk aluminosilicate glass containing silver particles is demonstrated. A diffraction efficiency of 1.5% is achieved for readout at the same wavelength. The speed of grating formation as a function of pulse energy suggests that two-photon excitation is responsible for the recording. The light causes bleaching of an absorption peak near 417 nm, which corresponds to the excitation of surface plasmons on the silver, and broad darkening throughout the visible to the near infrared. A likely mechanism for the photochromic effect is discussed.

Combinatorial topology, also known as "rubber sheet geometry", has extensive applications in geometry and analysis, many of which result from connections with the theory of differential equations. A link between topology and differential equations is vector fields. Recent developments in scientific visualization have shown that vector fields also play an important role in the analysis of second-order tensor fields. A second-order tensor field can be transformed into its eigensystem, namely, eigenvalues and their associated eigenvectors without loss of information content. Eigenvectors behave in a similar fashion to ordinary vectors with even simpler topological structures due to their sign indeterminacy. Incorporating information about eigenvectors and eigenvalues in a display technique known as hyperstreamlines reveals the structure of a tensor field. The simplify and often complex tensor field and to capture its important features, the tensor is decomposed into an isotopic tensor and a deviator. A tensor field and its deviator share the same set of eigenvectors, and therefore they have a similar topological structure. A a deviator determines the properties of a tensor field, while the isotopic part provides a uniform bias. Degenerate points are basic constituents of tensor fields. In 2-D tensor fields, there are only two types of degenerate points; while in 3-D, the degenerate points can be characterized in a Q'-R' plane. Compressible and incompressible flows share similar topological feature due to the similarity of their deviators. In the case of the deformation tensor, the singularities of its deviator represent the area of vortex core in the field. In turbulent flows, the similarities and differences of the topology of the deformation and the Reynolds stress tensors reveal that the basic addie-viscosity assuptions have their validity in turbulence modeling under certain conditions.

We report what we believe to be the first observation of photorefractive gratings in lead barium niobate (Pb(1-x)Ba (x)Nb(2)O( 6) ; PBN). A diffraction efficiency of 9% and a beam-coupling coefficient of 9 cm(-1) are obtained. After thermal fixing a grating of 0.5% is revealed at room temperature. We can improve this diffraction efficiency by optimizing fixing temperature, timing, and material parameters.

Ce doped and undoped SrxBa1-xNb2O6 (SBN) fibers grown by the laser heated pedestal growth (LHPG) technique in Stanford University were investigated by 2D scanning electron microprobe analysis. The SBN fibers grown along c [001] or a [100] axes often show radially distributed optical inhomogeneities (core effects) of varying magnitude. Ba enrichment and Sr reduction were primarily detected in the core which can be qualitatively described by a complex-segregation effect. This defect structure as a complex-congruency related phenomenon modified by the composition-control mechanism of LHPG system. Its radial dependence of effective segregation coefficient is described by the modified Burton-Prim- Slichter equation.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Volume holographic data storage is a promising alternative to current surface storage technologies, since it can provide simultaneously large digital storage capacity, fast data transfer rates, and short access times [1]. This is achieved by storing multiple holographic data pages in a common recording volume, while retaining the ability to retrieve any individual page. Multiplexing of data pages can be performed either at one wavelength, using angular or phase-encoded multiplexing, or at different wavelengths, using wavelength multiplexing. This investigation focuses on phase-encoded multiplexing, which for example allows direct binary arithmetic operations on recorded pages and enables data encryption [2].

Page-access optical memories are being investigated for the next generation of digital storage due to their potential for simultaneously achieving high capacity, fast transfer rates, and short access times. Examples of such memories are systems based on volume holography[1], two photon 3D recording[2], and spectral hole burning[3]. A common feature of these systems is that data is input using a spatial light modulator (SLM) and the output signal is imaged onto a CCD array. A typical arrangement for a digital volume holographic memory is shown in Fig. 1. To meet the capacity and transfer rate goals of a commercial system, page sizes on the order of one million pixels are required. The need to image pixel-to-pixel from the SLM to the CCD array over such a large page imposes tight tolerances on the optical design. Deviations from ideal imaging typically result in degraded performance. In future systems, signal processing methods will be required to overcome the limitations of the optical components. We describe a technique for data detection in page-acces memories that extends the well-known method of sequence detection from digital communications to two dimensions. The technique, which we term Decision Feedback Viterbi Algorithm (DF-VA) Detection improves the bit-error-rate (BER) performance of systems without ideal optics. Use of such a detection scheme can allow the use of less expensive, lower-complexity imaging optics, or, alternatively, can lead to higher information density per data page.

The performance of digital holographic data storage (DHDS) systems is primarily limited by the recording medium, as other components have been developed for consumer applications. In this invited paper we review state-of-the-art DHDS systems, fixing issues, and fundamental tradeoffs between materials and device characteristics. Recent results, including stored and retrieved video clips will be presented.

The lack of a suitable recording material has long been the Achilles heel of holographic storage. In contrast to the other system components (such as SLM, laser and detector array) which are generally available, although they may not be optimized for this particular application, the ideal material has yet to be developed. As a result, after 30 years of on-and-off development, no commercial digital holographic storage system has yet been deployed To address this bottleneck, the PRISM (photorefractive information storage materials) consortium was formed in 1994 to focus on the development of a suitable recording material and to understand how storage system trade-offs are affected by each candidate material system.

We discuss the experimental performance of a digital holographic data storage device and architectural and materials issues related to achieving large capacity and low bit error rates.

Epitaxial SBN:61 films have been grown on SBN:75 and MgO substrates by pulsed laser deposition. The optical loss due to absorption is greatly reduced by increasing the oxygen pressure to 1 mbar during the cooling process. In homoepitaxy, X-ray phi scans on the (221) plane of the SBN:61 films indicate that the in-plane grains are rotated 0° or ±28° with respect to single crystalline SBN:75 substrates. Cross-section and plane view high resolution TEM reveals this crystalline relations and microstructure of SBN thin films. Pr doped SBN:61 thin films show sharp transition band at 495 nm and 607 nm in room temperature photoluminescence measurement.

A volume photorefractive optical memory architecture can be integrated into 2D arrays of reconfigurable optical interconnect pixels for high performance digital processing applications such as high speed telecommunications and computing. This volume memory array will ultimately be implemented into a high performance optical computing module architecture. These modules use planar diffractive optical interconnect elements where fixed programs are stored. The insertion of volume photorefractive optical interconnect element technology will provide wavelength selective interconnect reconfigurability at system clock speeds (or faster). Target switching speeds of 1 ns may be achieved by electrical tuning of a multisection distributed Bragg reflection edge or a vertical cavity surface emitting laser diode. This photonic random optical memory access system is referred to as `PROMAC'.

Holograms may be superimposed in a holographic medium by a number of techniques such as angular, phase-encoded, and wavelength multiplexing. For typical architectures, crosstalk increases as the bandwidth of stored data increases. The number of superimposed holograms in an ideal medium is limited by its length L, the wavelength of light (lambda) , and index of refraction n, such that for crosstalk-limited storage we can superimpose up to 2nL/(lambda) holograms of high bandwidth. In practice, however, the properties of real materials depart from the ideal through index inhomogeneities and scattering centers, dispersion in the material response as a function of grating spatial frequency, and dispersion as a function of the wavevector and polarization of both incident and scattered light. We discuss the impact of these properties on holographic data storage and describe material, device, and system strategies designed to minimize these effects.

Color holography is typically achieved through the use of three wavelengths during the imaging. However, three-color holography is sufficient only when one has the freedom to select locally the proportions of the primaries during reconstruction. This freedom exists in some, but not all, holographic techniques; we discuss wavelength selection in light of this distinction. For holograms that do not allow for local control of color, such as display holography, the color contributions depend on the surface reflectances in the scene; the monochromatic sources point sample these reflectances. From this sampling, we show that the problem of wavelength selection is equivalent to that of finding efficient approximations to the tristimulus integrals. We conclude that three sources are often insufficient for accurate color reproduction, and we suggest wavelengths for holography with three, four, or more wavelengths. For holograms that do allow for local color control, the color science involved is similar to that of raster displays. Therefore, only three primaries are necessary. However, we describe situations where only two primaries are sufficient. This conclusion follows from the dichromatic theory of color reflection, which postulates that often the reflection of light from a surface contains only two color components.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this invited paper we discuss recent advances in holographic data storage using ferroelectric SBN fibers as the recording medium. An optical architecture involving an array of SBN fibers is discussed that potentially allows 2-3 orders of magnitude faster access times than for conventional magnetic data storage devices of Gbyte-size . To realize this potential we are studying the interplay between fundamental materials issues related to fiber growth and photorefractive processes underlying storage and readout processes in SBN.

We report the epitaxial growth of Sr0.6iBa0.39Nb2O6 (SBN) thin films on MgO substrates by pulsed laser deposition. Rutherford backscattering analysis shows that the films have stoichiometric composition, identical to the target, and thicknesses in the range 200–400 nm. X-ray diffraction 2θ-scans indicate layers with the (001) orientation perpendicular to the substrate plane, and phi scans on the (221) plane reveal that the films have two pairs of in-plane orientations. The orientations correspond to a rotation of the SBN unit cell relative to the MgO unit cell of ± 18.6° and ± 30.9° respectively. Waveguide characterization shows waveguides supporting up to four modes and film refractive indices which compare well with those of bulk SBN.

The capacity of volume holographic data storage depends on the multiplexing efficiency of input holographic data arrays or pages. We compare this page-packing capacity of two common approaches: angle, and wavelength multiplexing. For maximal page packing the angular separation between the reference and signal beam incidence in the angle and wavelength multiplexing methods should be 90 degree(s) and 180 degree(s), respectively. We find that in these optimal arrangements both methods can multiplex a similar number of paraxial data-page signals, which is comparable to conceptual storage capacity limits derived from considerations of resolution in three-dimensions. In practice, the high number of multiplexed data pages predicted here will be compromised by material-related noise sources.

The combination of large electro absorptive effects in semiconductor multiple quantum wells (MQW) and photorefractive-like transport offers the promise of producing fast, efficient thin film dynamic holographic materials for such applications as compact free space interconnects and high speed optical processors.1

Summary not available at time of printing.

Summary not available

Future optical communication and computer interconnect systems will require complex switching networks. Computer applications, in particular, may require monolithic, non-blocking switching networks of at least 100 × 100 elements. Numerous integrated-optical switch designs have been described and demonstrated with low insertion losses and high switching speeds.1 To . date, however, the highest level of integration achieved is a 16 × 16 LiNbO3 switch array on a 60 mm long substrate.2 One reason why these switch designs can’t be integrated to higher levels is the geometry of the basic device which consists of waveguides running in parallel or crossing at very small angles. This results in a device cell which is very long and thin and thus does not efficiently use substrate area. In addition, the near parallel waveguide geometry usually mandates the use of bends for waveguide separation which further increase overall switch area.

The objective of this tutorial is to explore similarities and differences between the design of conventional and integrated optical elements.

To avoid erasure of holograms, recorded in photorefactive materials, during readout several fixing techniques have been used.

The diffraction efficiency of a grating during recording and readout can be quite different from a simple exponential or double exponential behaviour predicted by the Kukhtarev model.

We demonstrate the all-optical recording of deeply subwavelength data bits in Ge2Sb2Te5 using a near-field scanning optical microscope (NSOM) probe that utilizes a C-aperture fabricated using through membrane focused ion beam milling. Data bits recorded with various optical powers were read out optically by C-aperture NSOM and the physical bit size was measured by atomic force microscopy (AFM). Both optical and AFM measurements were found to be in excellent agreement with simulation. We achieved a minimum physical bit size of 53.5×50.2 nm2 at a wavelength of 980 nm (λ/20) indicating a data density of 223 Gbit/in.2.

A polymeric light delivery system with a C-shaped metallic nanoaperture is proposed for the heat-assisted magnetic recording. This light delivery system has high optical efficiency and easy fabricability in the low temperature process that is compatible with the conventional magnetic head. The light delivery characteristics are demonstrated analytically and experimentally. In particular, the near-field spot size of the light delivery system was measured using the virtual scanning near-field optical microscopy (VSNOM) method, in which the probe tip geometry is not reflected. The probable spot size of the developed light delivery is under 100 nm at a wavelength of 780 nm from a polymeric light delivery with the C-shaped metallic nanoaperture.

In this paper we discuss recent advances in holographic data storage using ferroelectric SBN as the recording medium. A novel optical architecture involving an array of SBN fibers is discussed that allows 2 - 3 orders of magnitude faster access times than for conventional magnetic data storage devices of Gbyte size. To realize this potential we are studying fundamental materials issues related to SBN fiber growth and photorefractive processes underlying prolonged readout in SBN.

Cell-based polygonal isosurface generation is a common and useful technique for visualizing sampled scalar fields. Typically, however, the number of polygons in the surface model can become quite large as the size of the data set increases. In this paper, we present octree pruning techniques designed to compress the isosurface model while maintaining an accurate representation. We show results for several data sets, and demonstrate speed improvements of over two orders of magnitude over our previous results. A key feature of this work is the use of a volumetric error criterion to quantify model accuracy.

In this review we discuss photorefractive effects associated with holographic storage in ferroelectrics from a materials, optical architecture and systems viewpoint. As a guide to the discussion a holographic storage system based on phase encoding for multiple superposition of interconnect patterns is presented. System performance is evaluated in terms of storage capacity, cross talk between superimposed patterns, S/N ratio, erasure upon readout, recording, erasure, and cycle times, and sensitivity. These performance characteristics are intimately related to materials properties and photorefractive processes in ferroelectrics. For example, cross talk between superimposed interconnect patterns is dependent, among other things, upon striations in the medium, the specifics of the multiplexing scheme, and the application of fixing procedures. Material inhomogeneities may be overcome by using phase conjugate readout techniques, and phase encoding allows many more holograms to be superimposed than is practical with angular encoding. Fixing may be achieved by recording at elevated temperatures, and the efficiency and duration of readout is affected by application of an electric field. These phenomena are re viewed in terms of the dependence of fundamental electro-optic properties on such parameters as applied field and temperature. Examples are given of experimental and modeling results.

In this presentation we review recent advances in growth, evaluation, and application of photorefractive fibers for optical signal processing and data storage. Optical ferroelectric fibers are attractive alternatives to bulk photorefractives, because optical energy can be confined over longer interaction lengths, and fibers of good optical quality are easier to grow than bulk crystals, at least for certain morphologies. Since the material properties and the applications for which these fibers can be used are closely related, we will discuss both topics. Wave interactions in photorefractive fibers are discussed from a theoretical viewpoint, and applications, such as beam coupling in periodically poled fibers, stimulated back scattering in c-axis SBN fibers, and data storage in a-axis SBN fibers, including consideration of cross talk for multiplexed holograms are presented. The dependence of hologram cross talk on striations and other compositional variations in fibers is considered, and ways to overcome these problems are discussed.

A two-element aspheric objective lens having numerical aperture (NA) of 0.8 has been designed for media interchangeable holographic recordings. Lens design tolerance of offence against the sine condition and lens aberrations of object and reference beams have been formalized by coupled wave theory and related to diffraction efficiency of holograms. An optimum first-order power arrangement of objective lenses having two air-spaced elements has been identified by minimizing fifth-order aberrations and is further optimized ray-trace-based optimization code. Within tolerances criteria required for media-interchangeable systems, the design has demonstrated high NA of 0.8 with long working distance of 20% of the focal length.